Mystery gear shift failure

A 2004 Transalp 650 went superbly until a week ago. After the trip the bike was parked safely... in neutral. Well covered and in garage..... so 'warm, safe and dry'.
This morning an easy start and gave few minute for lekka idling for a proper 'wake-up for get-up and go'. Aaaand dammit there you go... freezed gearbox. Just cannot shift into a gear. What de hell??? Any pre-Christmas speculation???
Merry Christmas to all and to those who give to your life.